Adding the Particle 는:
Since both 저 and 나 end in a vowel (with no 받침), we can happily use 는 for both.
(For a noun with 받침, we use 은. 는 and 가 have the same function. Which one you use simply depends on whether or not a noun ends in 받침. This is the same concept as using "a/an" in English depending on if a noun starts with a vowel or consonant sound.)
저+는 -> 저는 -> 전
나+는 -> 나는 -> 난
(BONUS: 너+는 -> 너는 -> 넌)
The last arrow shows the contracted form. Both the full form and contraction can be used naturally, although, since it's humble, I see the contracted form of 저는 (전) less often than the contracted form of the casual 나는 (난) and 너는 (넌).
The meaning of 저는/전 is still "I/me" (humble).
The meaning of 나는/난 is still "I/me" (regular/lower).
The meaning of 너는/넌 is still "you" (regular/lower).
To understand the nuance, you must study and practice 은/는.
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Adding the Particle 를:
Since both 저 and 나 end in a vowel (with no 받침), we can happily use 를 for both.
(For a noun with 받침, we use 을. 를 and 을 have the same function. Which one you use simply depends on whether or not a noun ends in 받침. This is the same concept as using "a/an" in English depending on if a noun starts with a vowel or consonant sound.)
저+는 -> 저를 -> 절
나+는 -> 나를 -> 날
(BONUS: 너+를 -> 너를 -> 널)
The last arrow shows the contracted form. Both the full form and contraction can be used naturally, although, since it's humble, I see the contracted form of 저를 (절) less often than the contracted form of the casual 나를 (날) and 너를 (널). 날 can also mean "day". I feel like 널 is in a lot of songs.
The meaning of 저를/절 is still "me" (humble).
The meaning of 나를/날 is still "me" (regular/lower).
The meaning of 너를/널 is still "you" (regular/lower).
To understand the nuance, you must study and practice 을/를.
However, 을/를 is very straightforward so I will debrief you here and now.